A photonic integrated circuit (PIC) includes monolithically integrated photonic devices or elements and is useful as an optical data link in applications such as optical communications and high performance computing. For mobile computing platforms too, PICs offer a promising I/O for rapidly updating or syncing a mobile device with a host device and/or cloud service. Such optical links utilize an optical I/O interface that includes an optical transmitter and/or an optical receiver including one or more optical waveguide propagating light through one or more passive or active photonic device.
PICs are preferred to optical systems built with discrete optical components due to their compact size, lower cost, and the heightened functionality and/or performance. Silicon Photonics (SiPh) technology has clear advantages in terms of manufacturability and scalability. Lasers may be included in a transmitter or transceiver PIC. For SiPh technology, a hybrid silicon laser may be utilized which includes a compound semiconductor (e.g., III-V) gain medium bonded to, or epitaxially grown on, a silicon semiconductor device layer.
DFB laser architectures typically have a symmetric output (i.e., the same amount of light comes out both ends of the laser), which is disadvantageous in most optical systems because only one end of the laser is functionally coupled to other components in the optical system. For optical systems built with discrete optical components, a high-reflection coating (e.g., metal coating) may be applied to one end of a DFB laser to avoid wasting the other portion of the laser output not coupled to the optical system. This solution is not often practical for PICs, however.
DFB laser architectures also often suffer from a phenomenon known as “spatial hole burning” (SHB), which degrades laser performance over temperature as well as output power, and/or mode stability. The SHB effect stems from a highly asymmetric photon distribution and electric field distribution.
DFB laser architectures that address these limitations while remaining manufacturable are therefore advantageous.